In the Shipwrecked DLC, equipping Willow's Lighter while rowing on a boat may cause the lighter to still give off light without actually having the lighter equipped. This is fixed by restarting the game or dying.
Willow holding her lighter.
Willow's lighter on the ground.
If any character but Willow is given her lighter via Console.
Comparison of the light from Willow's Lighter and that from a torch
Willow's lighter has a very small light radius, barely keeping Chester inside it even though he's right next to her.
Cameo of Willow's Lighter in From the Ashes (on the second shelf from the top).
Willow's Lighter as seen in a drawing from Art Stream # 43.